Method for casting and rolling of metal stands from the casting heat

ABSTRACT

A method and apparatus for continuously casting metal in particular, steel rods, includes a continuous casting mold in which the rod is continuously cast and cooled to solidification as it is passed through the mold and moved through a transport path. The rod which is cast is subjected to a first set of up setting rolls and straightening rolls for reducing its cross section and for causing a stretching of the rod and a second set of high deformation rolls for further reducing the cross section and stretching the rod which is formed. The construction is characterized by an arrangement of the first acting sets of rollers at a first station to produce such a rod reduction and a rod stretching that the second acting rollers at the second station attain a maximum degree of deformation and at a faster passage rate of the rod which is cast and which therefore also requires a lower rolling force. The apparatus includes a roll stand for deforming the casting at a high reduction per pass which is preceeded by a roll stand having a roll gap which in the set in dependence upon the ratio of the casting cross section at the mold and the smallest possible rolling gap of the high deformation rollers. The construction is such that the casting cross section of the mold has a side ratio greater than 1 and the upsetting gap of the first roller set of approximately 1 and that of the high deformation stand of 1 or less than 1. The side ratio is the relationship of the side lengths with one another.

United States Patent 1 Baumann 1 Jan. 16,1973

[ METHOD FOR CASTING AND ROLLING OF METAL STANDS FROM THE CASTING HEAT [75] Inventor: Hans G. Baumann, Duisburg, Ger- [30] Foreign Application Priority Data Dec. 24, 1968 Germany ..P 18 16 849.5

[52] US. Cl ..164/76, 164/282 [51] Int. Cl. ..B22d 11/12 [58] Field of Search ..164/76, 82, 270, 282

[56] References Cited UNITED STATES PATENTS 2,714,752 8/1955 Wilson ..164/270 X 3,317,994 5/1967 Cofer et al ..164/76 3,358,358 12/1967 Jenks et al ..164/76 3,491,824 l/l970 Tarmann et al. ..164/76 3,543,555 12/1970 Baumann et a1 ..164/282 X FOREIGN PATENTS OR APPLICATIONS 950,882 2/1964 Great Britain ..164/282 173,322 ll/1960 Sweden ..164/82 Primary Examiner-R. Spencer Annear Attorney-McGlew & Toren [57] ABSTRACT A method and apparatus for continuously casting metal in particular, steel rods, includes a continuous casting mold in which the rod is continuously cast and cooled to solidification as it is passed through the mold and moved through a transport path. The rod which is cast is subjected to a first set of up setting rolls and straightening rolls for reducing its cross section and for causing a stretching of the rod and a second set of high deformation rolls for further reducing the cross section and stretching the rod which is formed. The construction is characterized by an arrangement of the first acting sets of rollers at a first station to produce such a rod reduction and a rod stretching that the second acting rollers at the second station attain a maximum degree of deformation and at a faster passage rate of the rod which is cast and which therefore also requires a lower rolling force. The apparatus includes a roll stand for deforming the casting at a high reduction per pass which is preceeded by a roll stand having a roll gap which in the set in dependence upon the ratio of the casting cross section at the mold and the smallest possible rolling gap of the high deformation rollers. The construction is such that the casting cross section of the mold has a side ratio greater than 1 and the upsetting gap of the first roller set of approximately 1 and that of the high deformation stand of 1 or less than 1. The side ratio is the relationship of the side lengths with one another.

2 Claims, 1 Drawing Figure METHOD FOR CASTING AND ROLLING OF METAL STANDS FROM THE CASTING HEAT SUMMARY OF THE INVENTION This invention relates in general to a method and apparatus for continuous casting and in particular to a new and useful method and apparatus in which the cast metal is subjected to a cross sectional reduction and stretching at a first station by upsetting rollers and straightening rollers and at a second station by a high deformation roller.

The invention is concerned in particular with the favorable arrangement for the casting and rolling of a continuous cast rod such as a steel rod which is formed by metal which is poured into a continuously operating casting mold and in which the rod is withdrawn; and during withdrawal, or directly adjacent the casting mold, the rod is subjected to cooling and solidification and thereafter to several deformation actions for reducing its cross section and causing a stretching.

In modern continuous casting installations, casting is followed by a rolling process in which the strands are rolled into bars. Formerly, such bars were rolled from slabs in heavy mills in a first step and then in billet mills in a second step. This method is used in many plants even today. By rolling strands from the casting heat, a second reheating process is unnecessary. Therefore, reheating furnaces were no longer needed. It was also possible to eliminate the requirement for billet mills.

Efforts have been made to increase the quantity of the rolling material which is obtained. This requirement results from given facts that the casting proceeds relatively slowly as does the cooling in a continuous casting process. The rolling device therefore operates in accordance with the speed of the casting installation. The yield of a greater quantity of material is therefore prevented by the naturally slow motor operation of such installations. In continuous casting installations having multiple veins for the casting flow this disadvantage is reduced in accordance with a number of such casting veins. However, the installation expenses increases the costs of the large number of roll stands which are necessary, so that the arrangement becomes exorbitant. The technical difficulty of arranging the roll stands for each vein side-by-side appears to be insolvable. Space is lacking for such a stand and for the drives which are required therefore. Large drive units are required depending on the stipulated forces in the economical path reduction which is necessary. Thus for the production of a cross section 70 by 70 milimeters at a casting cross section of 250 by 250 mm a ten stand continuous line is necessary and neither the costs nor the complicated construction is warranted.

Such a rolling mill train for 5 horizontal and 5 vertical stands would have to be provided for each casting vein. In the first stand a bloom of the dimensions of 250 by 250 mm would be tapped. The stands must be arranged alternately, horizontally and vertically. The end cross section of the rolled material is 70 by 70 mm. The output attained thereby is 235 tons per hour or 1,680,000 tons per year and a rolling speed of v 3.5 meters per second.

In accordance with the present invention means have been provided for avoiding the rolling on a multistrand trains and by an appropriate different working method.

The method at the same time increases the yield in comparison with conventional installations and also achieves advantages of the installation design obviating the mentioned disadvantages of spacial restriction.

In accordance with the invention, a method is proposed whereby the quantity of casting metal per unit of time is maintained at a maximum at a certain cross section formation and cooling output is arranged in conformity thereto and the metal being cast is then shaped with a maximum reduction per shaping pass. The rolling force required for the shaping of the metal is supplied in only two stations, the first providing a cross section reduction which causes such a stretching at the second station, that there is attained a maximum degree of deformation at a faster passage rate of the casting material but at a relatively smaller rolling force. The rolling force which for optimum deformation of the casting cannot be supplied by the high deformation machine alone is therefore made available in preceeding station so that the following high deformation operation can just take place.

Another advantage of the combination of pre-and after-deformation resides in the upsetting of the casting, that is, in an introductory transformation of the casting structure to a rolling texture.

The apparatus for carrying out the method is charac terized by a roll stand for deforming the casting which operates to effect a high reduction per pass and which is preceeded by a roll stand whose rolling gap between rollers is set in an independent ratio in respect to the cross section of the cast metal at the casting mold and also in respect to the smallest possible rolling gap which can be attained at the high deformation stand.

Accordingly, it is an object of the invention to provide an improved method for continuously casting and rolling, from casting heat, a continuous casting of metal, particularly steel, which comprises moving the continuously cast rod first into association with upsetting roll means and straightening roll means at a first station and thereafter into association with a high deformation roll means at a second station, the first cross sectional reduction is set to cause such a stretching of the rod that the second station may attain a maximum degree of deformation at a faster passage rate of the casting but at a relatively low rolling force.

A further object of the invention is to provide a continuous casting apparatus which includes a first station with upsetting and straightening rollers arranged to engage the continuous casting in a condition of casting heat, and a second station spaced from the first station having high deformation rollers arranged with a relatively small roll gap, and wherein the casting cross section advantageously has a side ratio greater than I and the upsetting roll gap at the first station, a side ratio of I, and that of the at the high deformation second station a side ratio of l or less than 1.

A further object of the invention is to provide a continuous casting device which is simple in design, rugged in construction, and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularly in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The only FIGURE of the drawing is a schematic side elevational view of a continuous casting and rolling device constructed in accordance with the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing in particular, the invention embodied therein comprises a combined continuous casting and rolling device which includes a continuous casting ladle or distributor trough 1 from which liquid steel or other metal flows into a continuous casting mold 2 in the form of a freely falling jet or in a jet guided in one or more immersion tubes. The mold 2 is made to oscillate in the casting direction in a known manner in order to bring about a favorable heat transfer between the casting material and the wall plates of the mold 2. In accordance with recent unpublished proposals the liquid portion 3 of the casting 4 need not extend into the region of the horizontal but may cool off with the aid of electrical or flow caused forces (not shown) in the manner illustrated in the drawing to cause solidification just behind the mold 2. The casting 4 is supported or moved by transport or feed rolls 5 and the movement may be entirely vertically or in a curve as indicated in the drawing into the region of the horizontal portion 6. The resulting structure of the casting material comprises a casting structure. Along the transport length of the continuous cast material the transport rolls 5 cause a more or less proportional force and provisions are generally made only to feed the casting away from the mold 2 and to transport it to the cooling section without causing any material changes in the cast structure and without internal or external damage thereto.

The cross section 8 of the casting will thus be maintained from the mold 2 up to a first station 50 for reducing the cross section and stretching the rod. The first station 50 includes a pair of upsetting rollers 9, 9' which are mounted in a roll stand having roller pressure adjustment means 11. In addition, a single pair of additional straightening rollers 10, 10 are located on extensions 54, 54 of the stand 52. The roll path 9, 9 and 10, 10' may have identical or differently acting diameters. The upsetting rolls 9, 9' can be pressed against the casting with considerable expenditure of force by means of the adjusting means 11 to a degree which brings about the destruction of the casting structure in external regions. At the same time, it is possible to drive the motors of the upsetting rolls 9, 9 and the straightening rollers 10, 10' at a speed of rotation to render the desired transmission of a ratio of compressive and tensile stresses.

Depending on the operational situations which occur, it is possible either to separate, or to combine with one another, the functions of upsetting and drawing or braking of the casting.

In the embodiment shown in the drawing the straightening rolls 10, 10' are only adjustable in respect to the casting and are not driven. The upsetting rolls 9, 9' produce besides their pressing efi'ect a required tensile or braking effect.

The casting 4 is thus pressed and brought to a certain density behind the upsetting rolls 9, 9' and then is moved into a high deformation machine generally designated 56. The high deformation machine 56 includes mounting frames l2, 12 arranged on respective opposite sides of the casting and each of which carries supporting rolls 13 and working rolls 14. An eccentric drive 15 and its associate linkage 58 provides a control for the positioning of the deformation rollers l4, 14'. An upsetting rather than a stretching effect is produced on the casting 4 but at the exit of the high deformation machine 56 these forces work as pure stretching forces. A reaction resulting therefrom which causes a temporary regulation of the stress ratio can readily be absorbed by the two or more upsetting roll pairs 9, 9'. The fluctuation of quality and the homogeneous nature of the casting can thus be compensated.

The casting issues as rolling material 16 which is guided between transport rollers on a simple roller bed 17 and it advantageously consists of a material which is already deformed to the extent that can be passed onto the known fine steel trains or depending on the requirements intermedium steel trains.

In order to practice the invention effectively, the continuous casting mold 12 is made of a very large cross section 8 in order to combine the highest possible cooling rates with the highest possible quantity of casting metal in such a way that the metal can still form metal structure which is free from inhomogeneities. The width of the strand which corresponds to the width of the cross section 8 and the width of the gap of the upsetting mill must both be in harmony with the width of the gap of the high deformation mill 56.

A ratio of the three mentioned passages to be suggested to the specialists should be selected, for example, that the cross section of the side lengths of the mold are 300 and 240 mm, the roll gap of the upsetting rolls stand 9 having a side ratio of 250 by 250 mm, while for reshaping the high deformation machine 12 side ratios of 200 by 200mm and less as desired should be provided.

For the high deformation machine 56 there is an intermediate heating system 20 or an insulation interval. A descaling device (not shown) may be provided instead of the heating system 20 or inserted ahead of it in order to meet the requirements for high deforming and especially to obtain a perfect material.

In an installation according to the invention the cross section of the cast material can be 300' by 240 mm which can be cast at a rate of v;l .04 meters per minute and be transferred to a roll stand which fulfills the function of a driver. In this driver the cross section of 250 by 250 mm is obtained. Thereafter in the second operation-the high deformation machine deforms the cross section to the final cross section of by 70 mm. Surprising the output of a single vein installation is about 570 kg per minute, that is, 34 tons per hour. This results in an annular production of 122,000 tons..

If one is to presuppose an abnormally high installation and operating costs (gravity discharge furnace operation with all apertaining measures and arrangements), a 10 stand Konti train with five horizontal and five vertical stands, there would indeed result, because of the independence from a continuous casting installation, a higher rolling speed (v velocity 3.5 meters per second). In the first stand a bloom of the dimension of 250 by 250mm would tapped. The stands would have to be arranged alternately, horizontally and vertically. The final cross section must again be taken to be 70 by 70 mm. Then there results an output of 235 tons per hour or 1,680,000 tons per year. Yet the costs per ton of steel is considerably higher. This is a known fact but it has not been possible until the present invention to solve the process problem of optimum adaptation between continuous casting installations and rolling arrangements.

The use of such Konti trains is thus excluded for reasons of cost and space. But also the cooperation between a continuous casting installation separate from the rolling train is not economical. A conventional continuous casting installation operates at a casting rate of 0.983 meters per minute with a casting cross section of 250 by 250 mm. The output of a single vein installation is approximately 467 kilograms per meter corresponding to 28 tons per hour. The annular output therefore is 100,000 tons of extruded steel. But even if the upsetting stand before the high deformation machine would be removed the harminizing effects of the two technological processes of casting and rolling attained with the installation according to the invention and by the method of the invention could not be achieved with success of the inventive method and apparatus. Assuring this case to occur, the calculation is as follows: the cross section of 250 by 250 mm is run into the high deformation machine and a casting rate of v 0.983 meters per minute and shaped to the final cross section of 70 by 70 mm. The output of the signal vein installation then is 467 kilograms per minute corresponding to the 28 tons per hour. Thus again one obtains an annual output of 100,000 tons which therefore is considerably lower than the output of a rolling arrangement including an upsetting mill (122,000 tons).

The production of the output of the casting rolling installation according to the invention constitutes an optimum between supply and fabrication of the casting material. It is appropriate to provide a dependent ratio of the cross sectional dimensions in all stations. According to the invention the casting cross section presents a side ratio of greater than 1, the upsetting rolling gap presents a ratio of l and that of the high deformation stand of l or less than 1.

During rolling, temperature variations within the range of plant practice. At relatively large quantities and long casting times, the melt material may cool off to such a degree that influences on the rolling behavior of the continuous casting are inevitable. Another condition results from the necessity of guiding the continuous casting correctly for rolling before the high deformation work cycle, that is, to supply a holding force in the casting direction. According to a special process the installation can be so operated that the casting tension between the high deformation stand and the upsetting stand is regulated by varying the speed of rotation of the rolls or by varying the working speed of the rolls of the high deformation stand 56.

The apparatus permits the formation of the casting so that its longitudinal sides may have a selected size in relation to the cross dimension or width to provide a related side ratio. For example, the geometrical surface of a rectangle requires inherently a side ratio which onl atpproaches one as a limit when it is the same as tha o a square, to wit 1:1. The apparatus of the invention may be constructed so that there is a side ratio of a preselected rectangular cross-section or a square crosssection. The casting mold may have a longitudinal side which is larger than the width. However, the upsetting roller nip, which is formed by the rollers 9,9, has a through-flow opening of square cross-section. By contrast, the nip of deformation rollers 14,14 frame is either square or rectangular. Of course, in respect to the term side ratio it is not determined in advance where the shorter or the longer side is to be situated. The shorter side may thus extend horizontally or vertically.

What is claimed is:

l. A method for the continuous casting and subsequent hot rolling from the casting heat of metal, particularly steel, comprising casting a strand of 300 by 240 mm at 1.04 meters per minute and subsequently subjecting the strand to reduction of its cross section and causing a stretching of the strand by a first pass at a first station edging the strand to 250 by 250 mm and in a second pass at a second station forming the strand by high deformation to a billet of by 70 mm of final cross section.

2. A method, according to claim 1, including heating the casting between said first station and said second station. 

1. A method for the continuous casting and subsequent hot rolling from the casting heat of metal, particularly steel, comprising casting a strand of 300 by 240 mm at 1.04 meters per minute and subsequently subjecting the strand to reduction of its cross section and causing a stretching of the strand by a first pass at a first station edging the strand to 250 by 250 mm and in a second pass at a second station forming the strand by high deformation to a billet of 70 by 70 mm of final cross section.
 2. A method, according to claim 1, including heating the casting between said first station and said second station. 